Many contemporary electronic devices have the facility to connect with external or peripheral audio devices. For instance, mobile telephones, tablets, laptop computers, mp3 players and the like are examples of electronic devices that are operable with peripheral audio devices such as a headset, for example, that is external to and distinct from the electronic device. A peripheral device such as a headset may typically comprise mono or stereo speakers for audio playback and possibly a microphone for voice communication.
Such external peripheral audio devices are often connected via a mating connector such as a plug and socket arrangement. For instance, many audio peripherals such as headsets have a jack plug such as a 3.5 mm jack plug for connection to a suitable jack socket on the host electronic device. A well-known arrangement for a jack plug and its associated socket is TRRS (Tip-Ring-Ring-Sleeve), which has four contacts for left audio, right audio, microphone, and ground. In one known arrangement, the tip (T) and first ring (R1) are used for left (L) and right (R) audio, for example left and right loudspeakers, with the second ring (R2) and sleeve (S) used for the microphone (M) and ground return (G) respectively. It will be appreciated that different arrangements for the left and right audio, microphone, and ground contacts are also possible. This provides for transfer of two channels of analogue audio data from the host device to the peripheral and transfer of a single channel of analogue audio data from the peripheral microphone to the host device.
Some peripherals devices such as headsets may comprise one or more microphone provided for noise cancellation, which may be distinct from, and thus additional to, any microphone provided for voice communication. For example a headset may include one or more additional microphones for detecting ambient noise so that compensating signals may be added to the playback audio to cancel out the ambient noise.
Typically the noise cancellation is performed in the peripheral itself. Thus the electronics to generate an appropriate cancellation signal may be provided in a headset itself, for instance in a dongle in the cable, wired to the multiple microphones. As power is required for the noise cancellation electronics the housing for the electronics may also need to include a battery, making it relatively bulky and heavy, which can be undesirable for a headset.
To avoid this, it has been proposed for the noise cancellation electronics to be provided in the host device, for instance a telephone handset. However, this would require extra connections via the audio jack to allow transfer of audio data from the noise cancelling microphones to the host device.
Various solutions have been proposed, and a common theme among several of them is the ability for a connector plug to be inserted into a connector socket in two or more different orientations. That is, the plug has at least two-fold rotational symmetry. See, for example, the Lightning™ connector produced by Apple Inc., or the USB type-C connector. For ease of use, it is important that the connection is operable in either orientation. A straightforward implementation of this idea is for each signal path in the peripheral device to be connected to multiple pins at rotationally symmetrical positions in the connector plug. Similarly, in the host device, signal paths may be coupled to multiple rotationally symmetrical pins in the connector socket. Thus, in this implementation, the orientation of the plug within the socket is irrelevant to the host device.
However, in many implementations it can be expected that more independent signal paths between the host device and the peripheral device will be needed (as discussed above) than can be handled by simply providing multiple pins for each signal path. Thus circuitry may be required to detect the orientation of the plug within the socket so that signals can be routed appropriately.
Further, there is a wide range of peripheral devices that may connect to the host device, each with different components and connection requirements. In some peripheral devices, for example, similar components may be connected to symmetrical pins of the connector, making it difficult to detect both the type of peripheral device that is connected, and the orientation of the plug within the socket.